The overall goal of this project is to investigate biochemical mechanism of how tolerance to and physical dependence upon barbiturates develop. The objective of this renewal application will focus on the role of GABAA and GABAB receptors in barbiturate tolerance and dependence. We will continue to utilize a rat model (intracerebroventricular, icv, infusion of pentobarbital) as an experimental model useful for determining how different binding sites [for GABA, benzodiazepines (BZ) and convulsants, e.g., picrotoxin and t-butylbicyclophosphorothionate (TBPS)] of the GABAA receptor complex and GABAB receptors in different regions of the brain are involved in chronic effects of pentobarbital.
The specific aims are designed to test the hypothesis formulated.
Specific Aim I. Characterization of GABAA receptors in different regions of the brain during the development of tolerance to and physical dependence upon pentobarbital. Studies on GABAA receptors in discrete areas of the brain will be the first step in gaining insight into the biochemical mechanisms of barbiturate actions. The investigations will be conducted at different time intervals during the development of tolerance to and physical dependence upon pentobarbital. The results obtained will be compared with those from acutely treated animals. The specific studies are as follows: 1. Biochemical characterization of different binding sites (GABA, BZ, TBPS) of the GABAA receptors; 2. Autoradiographic characterizations of different binding sites (GABA, BZ, TBPS) of the GABAA receptors; 3. In situ hybridization characterization of GABAA receptor subunit mRNA (alpha, beta, gamma, delta); and, 4. Cl- influx - functional characterization of GABAA receptors.
Specific Aim II. Characterization of GABAB receptors in different regions of the brain during the development of tolerance to and physical dependence upon pentobarbital. The specific studies are: 1. Biochemical characterization of ligand binding to GABAB receptors; and 2. Autoradiographic characterization of ligand binding to GABAB receptors.
Specific Aim III. Investigation of GABA release mechanisms in different regions of the brain during the development of tolerance to and physical dependence upon pentobarbital. The release of GABA affected by pentobarbital is intimately related to postsynaptic GABAA receptors and presynaptic GABAB receptors (autoreceptors).
Specific Aim I V. Systematic assessments of the degree of the development of tolerance to and physical dependence upon pentobarbital. The results obtained from these experiments will be correlated with the results derived from those of Specific Aims I-III.

Agency
National Institute of Health (NIH)
Institute
National Institute on Drug Abuse (NIDA)
Type
Research Project (R01)
Project #
5R01DA004480-08
Application #
2117218
Study Section
Drug Abuse Biomedical Research Review Committee (DABR)
Project Start
1987-09-01
Project End
1997-06-30
Budget Start
1994-08-01
Budget End
1995-06-30
Support Year
8
Fiscal Year
1994
Total Cost
Indirect Cost
Name
University of Mississippi Medical Center
Department
Pharmacology
Type
Schools of Medicine
DUNS #
928824473
City
Jackson
State
MS
Country
United States
Zip Code
39216
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Jang, C G; Oh, S; Ho, I K (1998) Changes in NMDAR2 subunit mRNA levels during pentobarbital tolerance/withdrawal in the rat brain: an in situ hybridization study. Neurochem Res 23:1371-7
Oh, S; Jang, C G; Ho, I K (1998) Activation of protein kinase C by phorbol dibutyrate potentiates [3H]MK-801 binding in rat brain slices. Brain Res 793:337-40
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Ito, T; Suzuki, T; Wellman, S E et al. (1996) Pharmacology of barbiturate tolerance/dependence: GABAA receptors and molecular aspects. Life Sci 59:169-95
Ito, T; Suzuki, T; Lim, D K et al. (1995) A novel quantitative receptor autoradiography and in situ hybridization histochemistry technique using storage phosphor screen imaging. J Neurosci Methods 59:265-71

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